1. Field of the Invention
The present invention relates to a composite material-stiffened panel to be applied to a wing and a tail assembly of an aircraft and a manufacturing method thereof.
2. Description of the Related Art
As a conventional stiffened panel, stiffened panels shown in FIGS. 1 through 4 are known.
A stiffened panel 10 shown in FIG. 1 is formed in such a manner that a skin 11 and a stiffener 12 are manufactured according to respective shapes, and they are bound to each other by a fastener 13 (rivet or the like).
A stiffened panel 10a shown in FIG. 2 is formed in such a manner that a skin 11a and a stiffener 12a are manufactured according to respective shapes, and they are bonded by an adhesive 14.
A stiffened panel 10b shown in FIG. 3 is formed in such a manner that a metal thick plate 15 shown by a dotted line is machined to be a stiffened panel (solid line).
A stiffened panel 10c shown in FIG. 4 is formed in such a manner that a composite material is formed into a stiffened plate by molding a skin 17 and a stiffener 18 integrally by means of a molding tool 16.
The method of manufacturing a stiffened panel by binding a skin and a stiffener by means of a fastener requires molding of the skin and the stiffener and provision of a positioning tool, thus resulting in high cost. Other problems are strict fastener design requirements (hole-edge distance and skin thickness for no sharp edges to a countersink) and reducing of fatigue strength due to a fastener-hole stress concentration.
The method of manufacturing a stiffened panel by bonding a skin and a stiffener by means of an adhesive requires molding of the skin and the stiffener, a pre-bonding process for the skin and the stiffener, positioning the skin and the stiffener, and provision of a pressurized holding tool for bonding, thus the cost becomes high.
The method of manufacturing a stiffened panel by machining a thick metal plate by machine working has a problem that since much of the material is cut and discarded, resources are wasted, and a problem that as weight efficiency is heightened, the cost of machine working becomes higher.
The method of manufacturing a stiffened panel by means of integral molding of a composite material has a problem of high cost factors such as provision of a complex tool for an accurately and integrally molded shape and of pressurizing the entire surface and an increase in scrap risk.